The invention relates generally to a method for predicting and compensating for shot peen distortion, and more particularly, to a method for predicting and compensating for shot peen distortion for objects having generalized geometries.
Shot peening is an industrial surface treatment routinely applied to reduce fatigue and consists of bombarding many small spherical hard particles onto a component surface, resulting in localized plastic deformation and residual compressive stresses. The resulting compressive surface stresses enhance fatigue and corrosion resistance but in some cases also introduce undesirable part distortion, which must be adequately compensated. Distortions are most problematic for components with thin-walled geometries that are subjected to high peening intensities, where the tolerance bands for the components are narrow.
A current method for compensating for part distortion involved peening the component twice. Briefly, a part is peened before a final machining, and then a light peen is performed on the newly machined surfaces. While this method can be used to produce satisfactory components, it undesirably requires additional manufacturing operations, thereby increasing costs and throughput times. Accordingly, it would be desirable to develop a method that compensates for shot peen distortion but does not require additional manufacturing operations.
Previous attempts have been made to model the effects of shot peening. However, the methods developed were tailored to solve sheet-metal forming problems, such as the contouring of aircraft wing-skins, and utilized only shell elements, or alternatively utilized only solid elements. Accordingly, neither of these models is adequate for the more general geometries of typical aircraft engine components, such as airfoils, rotating parts with thin flanges, thin-walled conical rotating sections, parts with true bolt locations that are applied after peening, and parts with seal teeth, or rabbit diameters that are applied after peening.
Accordingly, it would be desirable to develop a method that predicts and compensates for peening-induced distortion of objects with generalized geometries.